1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid droplets such as ink droplets to record an image on a recording material, and a method of manufacturing the head, more particularly to a liquid discharge head which records an image in an ink jet recording system.
2. Related Background Art
An ink jet recording system is one of so-called non-impact recording systems. In this ink jet recording system, noises generated during the recording are so small that they can be ignored, and high-speed recording is possible. In the ink jet recording system, the recording is possible with respect to various recording materials, ink is fixed to even so-called plain paper without requiring any special treatment, and a high-definition image can be obtained inexpensively. From such advantage, in recent years, the ink jet recording system has rapidly spread as not only a printer which is a peripheral of a computer but also recording means such as a copying machine, a facsimile machine, or a word processor.
As an ink discharge method of the ink jet recording system, there is a method in which an electrothermal transducing element such as a heater is used as a discharge energy generating element for use in discharging ink droplets. A principle is that a voltage is applied to the electrothermal transducing element to thereby bring the ink in the vicinity of the electrothermal transducing element to boil momentarily. Bubbles rapidly grow owing to a phase change of the ink during the boiling to thereby discharge the ink droplets at a high speed.
In Japanese Patent Application Laid-Open No. 4-10941, a discharge method is disclosed in which bubbles generated by driving the electrothermal transducing element in response to a recording signal are vented to outside air. Examples of a typical constitution for venting the bubbles to the outside air include a constitution in which the shortest distance between the electrothermal transducing element and a discharge port is largely shortened as compared with a conventional constitution.
There is a demand for a further increase of a recording speed in order to achieve a higher image quality output of a recorded image, a high quality level image, a high resolution output and the like with respect to a recording device provided with the above-described liquid discharge head.
In U.S. Pat. No. 6,158,843, there is disclosed a constitution in which a space where an ink channel is locally narrowed or a protrusion-like fluid resistant element is disposed in the vicinity of a supply port to thereby improve a flow of ink from the supply port to a supply path. According to such constitution, a discharge frequency can be enhanced, and the recording speed can be increased.
Additionally, in the above-described conventional liquid discharge head, when the ink droplets are discharged, a part of the ink with which a bubbling chamber is filled is pushed back into the supply path by means of the bubbles growing in the bubbling chamber. Therefore, the conventional liquid discharge head has a disadvantage that a discharge amount of ink droplets decreases with a decrease of a volume of the ink in the bubbling chamber.
Moreover, in the conventional liquid discharge head, in a case where a part of the ink with which the bubbling chamber is filled is pushed back into the supply path, a part of a pressure of the growing bubbles opposed to the side of the supply path escapes toward the supply path, or a pressure loss is generated by friction between an inner wall of the bubbling chamber and the bubbles. Therefore, the conventional liquid discharge head has a problem that a discharge speed of the ink droplets drops with a decrease of the pressure of the bubbles.
Furthermore, in the conventional liquid discharge head, a size of the discharge port is miniaturized in order to obtain the higher image quality output, higher quality level image, higher resolution output and the like. Therefore, there is a problem that the discharged ink is easily secured to the discharge port. The conventional liquid discharge head also has a problem that the ink discharged up to the discharge port is evaporated by atmospheric air on the surface of the discharge port, viscosity of the ink fluctuates, and discharge defects are generated.